The present invention relates to a display panel and a method for the manufacture thereof, in particular to a display panel using organic electroluminescent material and a method for manufacturing the same.
FIG. 7 illustrates an arrangement of luminescent picture elements in a conventional full-color display panel using organic electroluminescent material. As shown in FIG. 7, the conventional display panel has a plurality of luminescent picture elements 101 arranged in matrix manner. Each picture element 101 includes a red luminescent unit R, a green luminescent unit G and a blue luminescent unit B, all extending in a predetermined direction so as to form a stripe pattern on the display.
FIG. 8 illustrates the structure of a base section 101a mounting the luminescent picture elements 101. As shown in FIG. 8, the base section 101a has a plurality of first type electrodes 103 consisting of ITO, which are formed on the surface of one side of a transparent glass substrate 102. Further, a plurality of electrically insulating layers 104 and a plurality of electrically insulating partition walls 105 are provided at a predetermined interval over the first type electrodes 103 on the glass substrate 102, in a manner such that both the layers 104 and the walls 105 are orthogonal to and partially cover the electrodes 103.
Referring again to FIG. 8, a plurality of thin layers 106 of an organic electroluminescent material are formed in parallel with the layers 104 and partition walls 105 on exposed portions of the electrodes 103, a plurality of second type electrodes 107 are formed over the thin layers 106 so that both the electrodes 107 and the thin layers 106 are arranged in the same direction as the partition walls 105.
As shown in FIG. 8, the plurality of second type electrodes 107 are separated from one another by the partition walls 105 so as to prevent a possible electric short between two adjacent electrodes 107. Further, in order to exactly separate two adjacent electrodes 107, it is preferred that each partition wall 105 be formed to have an inverted trapezoidal cross section.
However, since both the electroluminescent layers 106 and the partition walls 105 are all apt to be affected by a moisture, it is necessary to provide a glass cover or a protection layer on the transparent glass substrate 102 to cover up the organic electroluminescent layers 106 and the partition walls 105, as shown in FIG. 9. FIG. 9a is a cross sectional view illustrating a display panel base section 101a including a plurality of picture elements which are sealed up by a glass cover 108. FIG. 9b is a cross sectional view illustrating a display panel base section 101a including a plurality of picture elements ire sealed up by a protection layer 109 having a moisture proof property.
In use, the first type electroeds 103 and the second type electrodes 107 are energized, so that some portions of the organic electroluminescent layers 106 corresponding to intersections of the first type electrodes 103 with the second type electrodes 107, are caused to emit lights which are displayed through the transparent glass substrate 102.
A process for manufacturing a display panel base section 101a may be described in the following with reference to FIGS. 10a-10c. 
At first, as shown in FIG. 10a, a plurality of first type electrodes 103 consisting of an electrically conductive transparent material such as ITO are formed on the transparent glass substrate 102. Then, a plurality of partition walls 105 are formed on the glass substrate 102. Each partition wall 105 has a cross section formed into an inverted trapezoidal shape having an overhang angle xcex8 with a vertical axis X.
Subsequently, as shown in FIG. 10b, with the use of a mask 111 punched in accordance with a predetermined pattern, the organic electroluminescent layers 106 corresponding to red luminescent unit R and green luminescent unit G and blue luminescent unit B, are formed on exposed portions of the first type electrodes 103.
Finally, as shown in FIG. 10c, a metal of low electric resistance such as Al, Cu or Au is vapor depositted on the organic electroluminescent layers 106 so as to form thereon a plurality of second type electrodes 107.
When the above metal is vapor depositted, the deposition direction is usually controlled to be perpendicular with respect to the substrate 102, so that the metal may be prevented from being depositted onto the side surfaces of the partition walls 105. In this way, the metal depositted on the top of each partition wall 105 is separated from adjacent second type electrodes 107, thereby preventing any possible electric short between two adjacent electrodes 107.
However, with the above method for producing a display panel, there is a possibility that some of the partition walls 105 will be partially broken, and another possibility that some fine contaminants or particles will attach to the side surfaces or the surrounding areas of the partition walls 105. As a result, when a metal is vapor depositted to form the second type electrodes 107, two adjacent electrodes 107 will be undesirably connected through the above fine contaminates or particles.
FIG. 11 is a cross sectional view indicating a condition where two adjacent electrodes 107 together with two organic electroluminescent layers 106 on both sides of a partition wall 105 are undesirably connected to each other through a mass of fine particles attached on the side surfaces of the partition wall 105. Accordingly, it is impossible to prevent electric short between two adjacent electrodes 107.
It is an object of the present invention to provide an improved display panel capable of exactly isolating two second type electrodes even if they are disposed very close to each other, so as to solve the above-mentioned problems peculiar to the above-mentioned prior art.
According to the present invention, there is provided an improved display panel using an organic electroluminescent material, comprising: a substrate; a plurality of first type electrodes formed on the surface of one side of the substrate; a plurality of electrically insulating partition wall groups each including a plurality of partition walls, partially covering and partially exposing the first type electrodes; a plurality of organic electroluminescent layers formed on exposed portions of the first type electrodes; and a plurality of second type electrodes formed on the organic electroluminescent layers. In particular, each partition wall group has one or more internal spaces each formed between two adjacent partition walls.
In more detail, there is provided an improved display panel which employs an organic electroluminescent material and in which a plurality of luminescent units are arranged in a matrix manner, said display panel comprising: a substrate; a plurality of first type electrodes arranged in parallel with one another at a predetermined interval on the surface of one side of the substrate; a plurality of electrically insulating partition wall groups each including a plurality of partition walls, partially covering and partially exposing the first type electrodes, arranged at a predetermined interval in a direction orthogonal to the first type electrodes on the substrate; a plurality of organic electroluminescent layers formed on exposed portions of the first type electrodes, arranged in parallel with said partition walls; and a plurality of second type electrodes formed on the organic electroluminescent layers in parallel therewith, each disposed between two adjacent partition wall groups. In particular, each partition wall group includes a plurality of partition walls arranged in parallel with one another at a predetermined interval, producing one or more internal spaces each formed between two adjacent partition walls.
In one aspect of the present invention, an elongated internal space is formed between every two adjacent partition walls, in a manner such that a cross section area over the elongate opening thereof is smaller than that at deep side.
In another aspect of the present invention, each partition wall has a cross section of overhung shape including a projecting upper portion projecting in a direction parallel with the substrate.
In a further aspect of the present invention, the projecting upper portion of each partition wall is higher than the height of the second type electrodes.
In a still further aspect of the present invention, prior to the formation of the partition walls, a plurality of electrically insulating layers are formed on the first type electrodes in the areas where the partition walls are to be formed, so that the electrically insulating layers are under partition walls and in surrounding areas.
In one more aspect of the present invention, the second type electrodes are formed by depositting a metal material on one side of the substrate after the formation of the first type electrodes and the partition walls and the organic electroluminescent layers, each internal space is so formed that the metal material is allowed to be smoothly depositted thereinto.
In one more aspect of the present invention, the substrate and the first type electrodes are all transparent.
Further, the present invention provides a method of producing a display panel using an organic electroluminescent material, comprising the steps of: forming a plurality of first type electrodes on the surface of one side of a substrate; forming a plurality of electrically insulating partition wall groups each including a plurality of partition walls, partially covering and partially exposing the first type electrodes, producing a plurality of internal spaces each formed between two adjacent partition walls; forming a plurality of organic electroluminescent layers on exposed portions of the first type electrodes; and forming a plurality of second type electrodes on the organic electroluminescent layers.
In one more aspect of the present invention, a mask means having a plurality of slit-like openings is placed over the tops of the partition walls, in a manner such that the slit-like openings are aligned with exposed portions of the first type electrodes between two partition wall groups, an electroluminescent material is depositted through the slit-like openings onto the first type electrodes, followed by moving the mask means onto the tops of other partition walls and depositting the electroluminescent material in the same manner so as to form a plurality of electroluminescent layers.
The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings.